/*
 * qrencode - QR Code encoder
 *
 * Masking for Micro QR Code.
 * Copyright (C) 2006-2011 Kentaro Fukuchi <kentaro@fukuchi.org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "config.h"
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <errno.h>

#include "qrencode.h"
#include "mqrspec.h"
#include "mmask.h"


__STATIC void MMask_writeFormatInformation(int version, int width, unsigned char* frame, int mask, QRecLevel level)
{
    unsigned int format;
    unsigned char v;
    int i;

    format = MQRspec_getFormatInfo(mask, version, level);

    for (i = 0; i < 8; i++)
    {
        v = 0x84 | (format & 1);
        frame[width * (i + 1) + 8] = v;
        format = format >> 1;
    }

    for (i = 0; i < 7; i++)
    {
        v = 0x84 | (format & 1);
        frame[width * 8 + 7 - i] = v;
        format = format >> 1;
    }
}

#define MASKMAKER(__exp__) \
    int x, y;\
\
    for(y=0; y<width; y++) {\
        for(x=0; x<width; x++) {\
            if(*s & 0x80) {\
                *d = *s;\
            } else {\
                *d = *s ^ ((__exp__) == 0);\
            }\
            s++; d++;\
        }\
    }

static void Mask_mask0(int width, const unsigned char* s, unsigned char* d)
{
    MASKMAKER(y & 1)
}

static void Mask_mask1(int width, const unsigned char* s, unsigned char* d)
{
    MASKMAKER(((y / 2) + (x / 3)) & 1)
}

static void Mask_mask2(int width, const unsigned char* s, unsigned char* d)
{
    MASKMAKER((((x * y) & 1) + (x * y) % 3) & 1)
}

static void Mask_mask3(int width, const unsigned char* s, unsigned char* d)
{
    MASKMAKER((((x + y) & 1) + ((x * y) % 3)) & 1)
}

#define maskNum (4)
typedef void MaskMaker(int, const unsigned char*, unsigned char*);
static MaskMaker* maskMakers[maskNum] =
{
    Mask_mask0, Mask_mask1, Mask_mask2, Mask_mask3
};

#ifdef WITH_TESTS
unsigned char* MMask_makeMaskedFrame(int width, unsigned char* frame, int mask)
{
    unsigned char* masked;

    masked = (unsigned char*)malloc(width * width);

    if (masked == NULL)
        return NULL;

    maskMakers[mask](width, frame, masked);

    return masked;
}
#endif

unsigned char* MMask_makeMask(int version, unsigned char* frame, int mask, QRecLevel level)
{
    unsigned char* masked;
    int width;

    if (mask < 0 || mask >= maskNum)
    {
        errno = EINVAL;
        return NULL;
    }

    width = MQRspec_getWidth(version);
    masked = (unsigned char*)malloc(width * width);

    if (masked == NULL)
        return NULL;

    maskMakers[mask](width, frame, masked);
    MMask_writeFormatInformation(version, width, masked, mask, level);

    return masked;
}

__STATIC int MMask_evaluateSymbol(int width, unsigned char* frame)
{
    int x, y;
    unsigned char* p;
    int sum1 = 0, sum2 = 0;

    p = frame + width * (width - 1);

    for (x = 1; x < width; x++)
    {
        sum1 += (p[x] & 1);
    }

    p = frame + width * 2 - 1;

    for (y = 1; y < width; y++)
    {
        sum2 += (*p & 1);
        p += width;
    }

    return (sum1 <= sum2) ? (sum1 * 16 + sum2) : (sum2 * 16 + sum1);
}

unsigned char* MMask_mask(int version, unsigned char* frame, QRecLevel level)
{
    int i;
    unsigned char* mask, *bestMask;
    int maxScore = 0;
    int score;
    int width;

    width = MQRspec_getWidth(version);

    mask = (unsigned char*)malloc(width * width);

    if (mask == NULL)
        return NULL;

    bestMask = NULL;

    for (i = 0; i < maskNum; i++)
    {
        score = 0;
        maskMakers[i](width, frame, mask);
        MMask_writeFormatInformation(version, width, mask, i, level);
        score = MMask_evaluateSymbol(width, mask);

        if (score > maxScore)
        {
            maxScore = score;
            free(bestMask);
            bestMask = mask;
            mask = (unsigned char*)malloc(width * width);

            if (mask == NULL)
                break;
        }
    }

    free(mask);
    return bestMask;
}
